WO2006075049A1 - Device for determining metallic contaminant particles in lubricating grease - Google Patents
Device for determining metallic contaminant particles in lubricating grease Download PDFInfo
- Publication number
- WO2006075049A1 WO2006075049A1 PCT/FI2006/000016 FI2006000016W WO2006075049A1 WO 2006075049 A1 WO2006075049 A1 WO 2006075049A1 FI 2006000016 W FI2006000016 W FI 2006000016W WO 2006075049 A1 WO2006075049 A1 WO 2006075049A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- lubricating grease
- contaminant particles
- determining
- metallic contaminant
- sample
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/26—Oils; Viscous liquids; Paints; Inks
- G01N33/28—Oils, i.e. hydrocarbon liquids
- G01N33/2835—Specific substances contained in the oils or fuels
- G01N33/2858—Metal particles
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/023—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance where the material is placed in the field of a coil
Definitions
- This invention relates to a device as defined in the preamble of claim 1 for determining the content of metallic contaminant particles in lubricating grease.
- the device using this method comprises a sampling pole at which the grease sample is placed, and an electric magnet which produces the first magnetic field.
- the device also comprises a second electric magnet which is used as a reference when the influence of the second magnetic field produced by the eddy currents induced in the sample are determined.
- This second electric magnet is identical to the first electric magnet and is preferably supplied from the same alternating current source as the first electric magnet.
- the device also comprises a measuring unit comprising a comparator and a amplifier.
- this previously known device uses a second electric magnet as a reference for inductance measurements, the device needs non-standard, expensive and large sized components. Also the use of a second electric magnet as a reference increases the power consumption of the device because of the resistive losses of the coil.
- the object of the invention is to overcome the drawbacks related to the device described above.
- Another object of the invention is to provide a new smaller, less expensive, and less power consuming device for determining the content of contami- nating particles, especially metal particles, in a lubricating grease.
- the device of the invention is characterized by the features defined in claim 1.
- the dependent claims set forth preferred embodiments of the invention.
- a sample is first taken to allow the determination to be made.
- the device comprises a sensor which comprises a core, on which the measured grease sample is placed, and a sensor coil which is wound around the core.
- the device also comprises an alternating current source for supplying the operating voltage.
- the device also comprises an inductance measurement bridge for determining the change of the impedance of the sensor coil, when a sample of lubricating grease containing contaminating particles is applied on the sensor, and for outputting a differential output signal to the outputs.
- the sensor coil is a part of the inductance measurement bridge.
- the device may also contain a rectifier bridge and a filter capacitor for rectifying and filtering the output signal from the measurement bridge.
- the invention has the advantage of the device being smaller sized and using less power. Another advantage of the inventions is that that the inexpensive mass produced passive components can be used instead of a comparison amplifier and a reference coil.
- figure 1 is a schematic view of the electric circuit of the device of the invention
- figure 2 is a view of the sensor of the device of the invention
- figure 3 is a schematic view of one user interface circuit of the invention
- figure 4 is a schematic view of another user interface circuit of the invention
- figure 5 is a schematic view of yet another user interface circuit of the invention
- figure 6 is a presentation of the voltage vectors of the circuit of the invention.
- the device of the invention utilizes the theoretical data of the method described in the Finnish patent application FI990393.
- a variation in the impedance of the sensor coil Ia can be measured by electric means. This is preferably carried out as follows:
- the device of the invention presented in figure 1 preferably comprises a sensor coil Ia, a measurement bridge 2 and an alternating current source 3.
- the sensor coil Ia is part of sensor 1, which has an electric magnet comprising a coil Ia wound around a core Ib as presented in figure 2.
- the measurement bridge 2 used for the determination of the impedance of the sensor coil is preferably a traditional Maxwell- Wien bridge.
- the measurement bridge is operated from an alternating current source 3.
- the alter- nating current has stabilized mean-effective-value, frequency and wave form. Due to the positive phase shift caused by the inductance L of the sensor coil Ia, the wave of the alternating electric current at the output terminal B of the measurement bridge 2 will be behind the wave of the alternating voltage supplied to the measurement bridge 2 by the alternating current source 3.
- the amplitude and phase shift of the output B of the measurement bridge 2 with respect to the operating voltage is defined by the sensor coil Ia (L+RL) and serial resistance R2.
- the capacitor C and its parallel resistor RC are chosen to outbalance the positive phase shift caused by the inductance of the sensor coil Ia. They have a negative phase shift so that the al- ternating current will be ahead of voltage of alternating current source 3. These can be seen from the voltage vectors presented in figure 6.
- the amplitude and phase shift of the output A of the measurement bridge 2 with respect to the operating voltage is defined by the capacitor C, parallel resistance RC and serial resistor Rl . If the capacitor C and the resistors RC and Rl are chosen ac- cording to the sensor coil Ia, the amplitudes and the phase shifts at both outputs A and B can be fixed to an appropriate basic level that gives a low basic output signal from the measurement bridge 2. That is the potentials at both outputs A and B are equal when the sensor coil Ia is outbalanced.
- the polarity of the basic output signal from the measurement bridge 2 must be the same as in a measurement situation.
- the amplitude and the phase shift at the output B changes with an increase in the apparent inductance of the sensor coil Ia when a grease sample having an amount of metal contaminating particles is placed on the core Ib, causing a potential difference between the two outputs (A-B). This increases the root-mean-square value of the output signal.
- the output signal from the outputs A and B is then rectified in a rectifier bridge 4.
- a filtering capacitor 6 is supplied for filtering the resulting DC current.
- the rectified and filtered signal can then be analyzed and the result of the analyze outputted to the user with one of the several possible types of arrangements in an user inter- face circuit 7.
- the simplest example of the user interface circuit 7 is a qualitative threshold display.
- a LED 9 in figure 3 can be illuminated when the voltage of the output signal exceeds a pre-set level. There can be several levels each level lighting a different colored LED 9. At the same time an audible alarm can be heard.
- the alarm level is adjusted by means of a variable resistor 8 when a calibration grease with a specific metal particle content is applied to the sensor coil Ia.
- the user interface circuit 7 is a quantitative display.
- This display can be a digital voltage displaying device 11 with an A/D-converter 10 as presented in figure 4, or a traditional coil instrument, or some other type of device ca- pable of displaying voltage signal levels. It indicates the metal particle content as a number that is relative to the apparent change in the inductance of a sensor coil Ia. It however does not express the metal particle content as such; the value can be compared with a given limit value for acceptable grease samples, or the value can be externally converted into a metal particle content by using a library of data ob- tained by previous or subsequent measurements on grease samples of known metal particle content.
- the third example of the user interface circuit 7 is an analytical equipment, which by means of software converts each measurement signal into a metal particle content.
- This equipment can for example be a microcontroller 13 having an AJO- converter input 12 as presented in figure 5.
- the result of the measurement is then displayed for example on a digital display 14.
- This equipment has to be calibrated by using grease samples of known metal particle content. In this calibration process a conversion table between voltage levels and metal particle contents is created and saved to be used by the software during measurements.
- This analyzer circuit has the advantage that the software can collect several measurement results and save them to a data file for later inspection.
- an amplifier can be added to the circuit before user interface circuit.
- the sensor coil Ia can be de-connected from the measurement bridge 2 between measurements. This also reduces further the power consumption of the measuring device, especially in portable devices.
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Pathology (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
This invention relates to a device for determining metallic contaminant particles in lubricating grease. In the device of the invention, a sample is first taken to allow the determination to be made. The device comprises a sensor (1) which comprises a core (1b), on which the measured grease sample is placed, and a sensor coil (1a) which is wound around the core. The device also comprises an alternating current source (3) for supplying the operating voltage. In accordance with the invention the device also comprises an inductance measurement bridge (2) for determining the change of the impedance of the sensor coil (1a), when a sample of lubricating grease containing contaminating particles is applied on the sensor (1), and for outputting a differential output signal to the outputs A and B.
Description
Device for determining metallic contaminant particles in lubricating grease
This invention relates to a device as defined in the preamble of claim 1 for determining the content of metallic contaminant particles in lubricating grease.
In order to reduce dynamic friction and wear in rotating or axially moving machine parts, for example bearings, these parts are treated with lubricating grease. In the course of time the properties of the lubricating grease deteriorates. This is due to the fact that impurities accumulate from the moving surfaces as they wear in to the grease. These impurities are mainly metallic particles because machines are mainly made out of steel or any other suitable metal. In order to ensure defect free operation, the interfaces of moving parts need to be cleaned and lubricating grease to be replaced at suitable service intervals.
There are several conventional methods for determining contaminant particles in lubricating grease. One example of these conventional methods is the examination of the lubricant sample with direct microscopy. This as well as other conventional methods are however laborious and slow. They are appropriately performed in laboratory environment and are not practical to perform under field conditions.
There are methods and devices for more easily determining the amount of contaminating particles, especially metallic particles, in lubricating grease.
In Finnish patent application FI990393, corresponding international application PCT/FIOO/00148, a method and a device for determining metallic contaminant particles in lubricating grease is described. According to this method a sample of lubricating grease is subjected to a first magnetic field which is alternating at a constant frequency. This first magnetic field induces eddy currents in the contaminant parti- cles occurring in the sample of lubricating grease. These eddy currents in turn produce a second magnetic field, which influences the first magnetic field by resisting its variations.
By inductance measurements, the apparent inductance of the coil, resulting from the interference caused by the contaminating particles in the grease sample, can be de- termined.
The device using this method comprises a sampling pole at which the grease sample is placed, and an electric magnet which produces the first magnetic field. In addition
of the first electric magnet the device also comprises a second electric magnet which is used as a reference when the influence of the second magnetic field produced by the eddy currents induced in the sample are determined. This second electric magnet is identical to the first electric magnet and is preferably supplied from the same alternating current source as the first electric magnet. In addition to these the device also comprises a measuring unit comprising a comparator and a amplifier.
Because this previously known device uses a second electric magnet as a reference for inductance measurements, the device needs non-standard, expensive and large sized components. Also the use of a second electric magnet as a reference increases the power consumption of the device because of the resistive losses of the coil.
The object of the invention is to overcome the drawbacks related to the device described above. Another object of the invention is to provide a new smaller, less expensive, and less power consuming device for determining the content of contami- nating particles, especially metal particles, in a lubricating grease.
The device of the invention is characterized by the features defined in claim 1. The dependent claims set forth preferred embodiments of the invention.
In the device of the invention, a sample is first taken to allow the determination to be made. The device comprises a sensor which comprises a core, on which the measured grease sample is placed, and a sensor coil which is wound around the core. The device also comprises an alternating current source for supplying the operating voltage. In accordance with the invention the device also comprises an inductance measurement bridge for determining the change of the impedance of the sensor coil, when a sample of lubricating grease containing contaminating particles is applied on the sensor, and for outputting a differential output signal to the outputs.
In the preferred embodiment of the invention the sensor coil is a part of the inductance measurement bridge. The device may also contain a rectifier bridge and a filter capacitor for rectifying and filtering the output signal from the measurement bridge.
The invention has the advantage of the device being smaller sized and using less power. Another advantage of the inventions is that that the inexpensive mass produced passive components can be used instead of a comparison amplifier and a reference coil.
The invention will be explained in detail below with reference to the accompanying drawing, in which
figure 1 is a schematic view of the electric circuit of the device of the invention; figure 2 is a view of the sensor of the device of the invention; figure 3 is a schematic view of one user interface circuit of the invention; figure 4 is a schematic view of another user interface circuit of the invention; figure 5 is a schematic view of yet another user interface circuit of the invention; and figure 6 is a presentation of the voltage vectors of the circuit of the invention.
The device of the invention utilizes the theoretical data of the method described in the Finnish patent application FI990393. A variation in the impedance of the sensor coil Ia can be measured by electric means. This is preferably carried out as follows:
The device of the invention presented in figure 1 preferably comprises a sensor coil Ia, a measurement bridge 2 and an alternating current source 3. The sensor coil Ia is part of sensor 1, which has an electric magnet comprising a coil Ia wound around a core Ib as presented in figure 2. The measurement bridge 2 used for the determination of the impedance of the sensor coil is preferably a traditional Maxwell- Wien bridge.
The measurement bridge is operated from an alternating current source 3. The alter- nating current has stabilized mean-effective-value, frequency and wave form. Due to the positive phase shift caused by the inductance L of the sensor coil Ia, the wave of the alternating electric current at the output terminal B of the measurement bridge 2 will be behind the wave of the alternating voltage supplied to the measurement bridge 2 by the alternating current source 3.
The amplitude and phase shift of the output B of the measurement bridge 2 with respect to the operating voltage is defined by the sensor coil Ia (L+RL) and serial resistance R2. On the opposite side of the measurement bridge 2 the capacitor C and its parallel resistor RC are chosen to outbalance the positive phase shift caused by the inductance of the sensor coil Ia. They have a negative phase shift so that the al- ternating current will be ahead of voltage of alternating current source 3. These can be seen from the voltage vectors presented in figure 6.
The amplitude and phase shift of the output A of the measurement bridge 2 with respect to the operating voltage is defined by the capacitor C, parallel resistance RC and serial resistor Rl . If the capacitor C and the resistors RC and Rl are chosen ac-
cording to the sensor coil Ia, the amplitudes and the phase shifts at both outputs A and B can be fixed to an appropriate basic level that gives a low basic output signal from the measurement bridge 2. That is the potentials at both outputs A and B are equal when the sensor coil Ia is outbalanced.
The polarity of the basic output signal from the measurement bridge 2 must be the same as in a measurement situation. In a measurement situation, the amplitude and the phase shift at the output B changes with an increase in the apparent inductance of the sensor coil Ia when a grease sample having an amount of metal contaminating particles is placed on the core Ib, causing a potential difference between the two outputs (A-B). This increases the root-mean-square value of the output signal.
The output signal from the outputs A and B is then rectified in a rectifier bridge 4. A filtering capacitor 6 is supplied for filtering the resulting DC current. The rectified and filtered signal can then be analyzed and the result of the analyze outputted to the user with one of the several possible types of arrangements in an user inter- face circuit 7.
The simplest example of the user interface circuit 7 is a qualitative threshold display. For example a LED 9 in figure 3 can be illuminated when the voltage of the output signal exceeds a pre-set level. There can be several levels each level lighting a different colored LED 9. At the same time an audible alarm can be heard. The alarm level is adjusted by means of a variable resistor 8 when a calibration grease with a specific metal particle content is applied to the sensor coil Ia.
Another example of the user interface circuit 7 is a quantitative display. This display can be a digital voltage displaying device 11 with an A/D-converter 10 as presented in figure 4, or a traditional coil instrument, or some other type of device ca- pable of displaying voltage signal levels. It indicates the metal particle content as a number that is relative to the apparent change in the inductance of a sensor coil Ia. It however does not express the metal particle content as such; the value can be compared with a given limit value for acceptable grease samples, or the value can be externally converted into a metal particle content by using a library of data ob- tained by previous or subsequent measurements on grease samples of known metal particle content.
The third example of the user interface circuit 7 is an analytical equipment, which by means of software converts each measurement signal into a metal particle content. This equipment can for example be a microcontroller 13 having an AJO-
converter input 12 as presented in figure 5. The result of the measurement is then displayed for example on a digital display 14. This equipment has to be calibrated by using grease samples of known metal particle content. In this calibration process a conversion table between voltage levels and metal particle contents is created and saved to be used by the software during measurements. This analyzer circuit has the advantage that the software can collect several measurement results and save them to a data file for later inspection.
If the rectified and filtered output signal is too weak before analyzing, an amplifier can be added to the circuit before user interface circuit.
In order to reduce any thermal effects on the grease sample, and its softening due to this, the sensor coil Ia can be de-connected from the measurement bridge 2 between measurements. This also reduces further the power consumption of the measuring device, especially in portable devices.
For the one skilled in the art it is obvious that the preceding example does not limit the scope of the invention, and that the different alternatives of the invention are defined by the claims.
Claims
1. A device for determining metallic contaminant particles in lubricating grease, a sample being taken for determination, the device comprising:
- a sensor (1) comprising a core (Ib), on which the measured grease sample is placed, and a sensor coil (Ia) wound around the core (Ib); and
- an alternating current source (3) for supplying the operating voltage;
characterized in that, the device further comprises:
- an inductance measurement bridge (2) for determining the change of the impedance of the sensor coil (Ia), when a sample of lubricating grease containing con- taminating particles is applied on the sensor (1), and outputting a differential output signal to the outputs (A and B).
2. A device for determining metallic contaminant particles in lubricating grease according to claim 1, characterized in that, the sensor coil (Ia) is a part of the inductance measurement bridge (2) on one side, and the capacitor (C) and parallel re- sistor (RC) are part of the inductance measurement bridge (2) on the opposite side.
3. A device for determining metallic contaminant particles in lubricating grease according to claim 1 or 2, characterized in that, the device further contains a rectifier bridge (4) and a filter capacitor (6) for rectifying and filtering the output signal from the measurement bridge (2).
4. A device for determining metallic contaminant particles in lubricating grease according to claims 1, 2 or 3, characterized in that, the device further comprises an amplifier (5) for amplifying the rectified and filtered output signal.
5. A device for determining metallic contaminant particles in lubricating grease according to any of claims 1-4, characterized in that, the device further comprises an user interface circuit (7) for analyzing the rectified and filtered output signal and outputting the result to the user.
6. A device for determining metallic contaminant particles in lubricating grease according to claim 5, characterized in that, the user interface circuit (7) is a qualitative threshold display.
7. A device for determining metallic contaminant particles in lubricating grease according to claim 5, characterized in that, the user interface circuit (7) is a quantitative display.
8. A device for determining metallic contaminant particles in lubricating grease according to claim 5, characterized in that, the user interface circuit (7) is an analytical equipment.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20050044 | 2005-01-14 | ||
| FI20050044A FI20050044L (en) | 2005-01-14 | 2005-01-14 | Apparatus for determining metallic impurity particles in lubricating grease |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2006075049A1 true WO2006075049A1 (en) | 2006-07-20 |
Family
ID=34112597
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/FI2006/000016 Ceased WO2006075049A1 (en) | 2005-01-14 | 2006-01-13 | Device for determining metallic contaminant particles in lubricating grease |
Country Status (2)
| Country | Link |
|---|---|
| FI (1) | FI20050044L (en) |
| WO (1) | WO2006075049A1 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017181036A (en) * | 2016-03-28 | 2017-10-05 | 東京電力ホールディングス株式会社 | Deterioration evaluation method for ultra minute amount of grease |
| DE102017211604A1 (en) | 2016-08-02 | 2018-02-08 | Aktiebolaget Skf | Bearing arrangement with a pollution sensor |
| CN110567860A (en) * | 2019-08-28 | 2019-12-13 | 广东工业大学 | Novel Particle Counter and Particle Counting Method |
| CN112986077A (en) * | 2021-02-05 | 2021-06-18 | 大连海事大学 | Novel bridge oil liquid measuring device for mechanical equipment health monitoring |
| CN113325047A (en) * | 2021-05-14 | 2021-08-31 | 大连海事大学 | Lubricating oil cleanliness monitoring device based on multi-parameter bridge method |
| CN113640185A (en) * | 2021-08-03 | 2021-11-12 | 中国科学院兰州化学物理研究所 | Device for rapidly measuring content of ferromagnetic wear particles in lubricating grease |
| CN116678774A (en) * | 2023-04-21 | 2023-09-01 | 中北大学 | Multi-stage split lubricating oil abrasive particle detection system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4731578A (en) * | 1985-05-02 | 1988-03-15 | Aeroquip Corporation | Electrical sensing system for measuring ferrous particles within a fluid |
| JPH06331600A (en) * | 1993-05-26 | 1994-12-02 | New Cosmos Electric Corp | Magnetic powder concentration meter |
| WO2000050883A1 (en) * | 1999-02-24 | 2000-08-31 | Valtion Teknillinen Tutkimuskeskus | Method and device for determining metallic contaminant particles in lubricating grease |
-
2005
- 2005-01-14 FI FI20050044A patent/FI20050044L/en not_active IP Right Cessation
-
2006
- 2006-01-13 WO PCT/FI2006/000016 patent/WO2006075049A1/en not_active Ceased
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4731578A (en) * | 1985-05-02 | 1988-03-15 | Aeroquip Corporation | Electrical sensing system for measuring ferrous particles within a fluid |
| JPH06331600A (en) * | 1993-05-26 | 1994-12-02 | New Cosmos Electric Corp | Magnetic powder concentration meter |
| WO2000050883A1 (en) * | 1999-02-24 | 2000-08-31 | Valtion Teknillinen Tutkimuskeskus | Method and device for determining metallic contaminant particles in lubricating grease |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017181036A (en) * | 2016-03-28 | 2017-10-05 | 東京電力ホールディングス株式会社 | Deterioration evaluation method for ultra minute amount of grease |
| DE102017211604A1 (en) | 2016-08-02 | 2018-02-08 | Aktiebolaget Skf | Bearing arrangement with a pollution sensor |
| US10378585B2 (en) | 2016-08-02 | 2019-08-13 | Aktiebolaget Skf | Bearing assembly with contamination sensor |
| CN110567860A (en) * | 2019-08-28 | 2019-12-13 | 广东工业大学 | Novel Particle Counter and Particle Counting Method |
| CN112986077A (en) * | 2021-02-05 | 2021-06-18 | 大连海事大学 | Novel bridge oil liquid measuring device for mechanical equipment health monitoring |
| CN112986077B (en) * | 2021-02-05 | 2022-11-29 | 大连海事大学 | Novel bridge oil liquid measuring device for mechanical equipment health monitoring |
| CN113325047A (en) * | 2021-05-14 | 2021-08-31 | 大连海事大学 | Lubricating oil cleanliness monitoring device based on multi-parameter bridge method |
| CN113325047B (en) * | 2021-05-14 | 2022-12-06 | 大连海事大学 | A monitoring device for lubricating oil cleanliness based on multi-parameter bridge method |
| CN113640185A (en) * | 2021-08-03 | 2021-11-12 | 中国科学院兰州化学物理研究所 | Device for rapidly measuring content of ferromagnetic wear particles in lubricating grease |
| CN116678774A (en) * | 2023-04-21 | 2023-09-01 | 中北大学 | Multi-stage split lubricating oil abrasive particle detection system |
Also Published As
| Publication number | Publication date |
|---|---|
| FI20050044A0 (en) | 2005-01-14 |
| FI20050044A7 (en) | 2006-07-15 |
| FI20050044L (en) | 2006-07-15 |
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